The present invention relates to a wiring board for mounting electronic parts, and in particular to a wiring board mounting chip capacitors on a reverse face side.
IC chips has become higher speed in actuation owing to progress of technique of integrated circuit, and being accompanied therewith, noises are accumulated on such as wiring of electric source and bring about erroneous actuation. For removing noises, for example, as seen in FIG. 22, a wiring board 2 mounting IC chip 1 thereon is separately mounted with chip capacitors 3 on a principal face 2b or a reverse face 2c, and capacitor-connecting wiring 4 is provided within the wiring board for respectively connecting two electrodes of the capacitors 3. Thereby, the chip capacitors 3 are connected to a source terminal or an earth terminal of IC chip 1 via the capacitor-connecting wiring 4 and flip-chip pad 5.
However, depending on the above technique, the capacitor-connecting wiring 4 connected to the chip capacitors 3 are drawn around within the wiring board 2. When changing positions of terminals of IC chip 1, it has been necessary to re-design a whole wiring including the capacitor-connecting wiring 4. Especially, IC chip of high integration degree is often formed with lots of source terminals and earth terminals, and the drawing-around is easily subject to complication. In addition, in case of mounting many chip capacitors or connecting the chip capacitors having many terminals, the drawing-around also becomes complicated.
The invention has been accomplished in view of these problems, and it is an object of the invention to provide a wiring board making ready for connecting electronic parts mounted on the principal face side of the wiring board with chip capacitors mounted on the reverse face side thereof.
Means for solving the problems is a wiring board having a principal face and a reverse face, comprising a plurality of principal-face-side connecting terminals formed on the principal face side and connectable to respective terminals of electronic parts to be mounted on the principal face side, chip capacitors mounted on the reverse face side furnished with a first electrode and a second electrode composing capacitors, at least one of the chip capacitors having a first face facing to the reverse face, at least one of first terminals formed on the first face and connected to the first electrode, and at least one of second terminals formed on the first face and connected to the second electrode, first capacitor-connecting terminals formed on the reverse face side and connected to the respective first terminals of the chip capacitors, second capacitor-connecting terminals formed on the reverse face side and connected to the respective second terminals of the chip capacitors, a plurality of insulating layers interposed among the principal-face-side connecting terminals, the first capacitor-connecting terminals, and the second capacitor-connecting terminals, at least one of first converting-conductor layers formed at specific interlayer selected from interlayers of the mutual insulating layers, connected to the plurality of principal-face-side connecting terminals at the principal face side, connected to at least one of first capacitor-connecting terminals at the reverse face side, and changing the connecting positions and the connecting number between the principal face side and the reverse face side, and at least one of second converting-conductor layers formed at the specific interlayer while being insulating the first converting-conductor layers, connected to the plurality of principal-face-side connecting terminals at the principal face side, connected to at least one of second capacitor-connecting terminals at the reverse face side, and changing the connecting positions and the connecting number between the principal face side and the reverse face side.
The wiring board of the invention is formed with the first and the second converting-conductor layers for changing the connecting positions and the connecting number between the principal face side and the reverse face side at the same specific interlayer. The first converting-conductor layers are connected to the principal-face-side connecting terminals at the principal face side, and to the first capacitor-connecting terminals at the reverse face side. Further, the second converting-conductor layers are connected to the principal-face-side connecting terminals at the principal face side, and to the second capacitor-connecting terminals at the reverse face side. Therefore, the connection between the principal-face-side connecting terminals and the first and second capacitor-connecting terminals is easily provided. Accordingly, the connection between terminals of the electronic parts and the first and second terminals is easily made.
As the chip capacitors, any of them are sufficient if being able to be mounted on the wiring board. For example, there are enumerated laminated ceramic types, electrolytic capacitor types, or film capacitor types. In particular, the chip capacitors of the laminated ceramic type have desirable frequency characteristics, and being effected with heat, the characteristics are comparatively stable.
Besides, the first and second terminals formed on the first faces of the chip capacitors are preferably many formed. Because, by forming many, those may be connected in parallel with the first and second converting-conductor layers, and resistance and inductance occurring at wiring between the first, second converting-conductor layers and the chip capacitors may be more reduced. Therefore, the first and second terminals of the chip capacitors are sufficient with those formed on the periphery of the first face, but preferable are such terminals arranged in, e.g., lattice within the first face.
More preferable are that the first terminal and the second terminal are alternately arranged in a manner that, seeing from a certain first terminal, a nearest terminal to this first terminal is a second terminal. The current flowing via the first terminal and the current flowing via the second terminal are opposite to each other with regard to direction when charging and discharging the chip capacitors, and also in this regard, inductance can be decreased.
As the wiring board, there are listed resins such as epoxy resin, polyimide resin, BT resin or PPE resin, composite materials of fibers such as glass fiber or polyester fiber with the resins, or resin composite materials of fluorine resin having three dimensional network structure impregnated with epoxy resin. Further listed are ceramic boards made of alumina, mullite, aluminum nitride or glass ceramic, or combinations of the ceramic board with the resins or composite materials.
Around the principal-face-side connecting terminals and the first and the second capacitor-connecting terminals, solder resist layers may be formed for securing the mutual insulation and preventing solder wetted spread.
In the wiring board as mentioned above, it is preferred that as the specific interlayer, the nearest interlayer to the first capacitor-connecting terminals and the second capacitor-connecting terminals among the interlayers of the mutual insulating layers are selected, and the number of the principal-face-side connecting terminals connected to any of the first converting-conductor layers and the second converting-conductor layers of the principal-face-side connecting terminals is more than the sum of the number of the first capacitor-connecting terminals connected to the first converting-conductor layers+(plus) the number of the second capacitor-connecting terminals connected to the second converting-conductor layers.
The wiring of connecting the principal-face-side connecting terminals and the first, second capacitor-connecting terminals (the first and the second terminals of the chip capacitors) can restrain resistance value and inductance, the more the parallel paths. Accordingly, seeing from the first and the second converting-conductor layers, a comparison is made between the number of the principal-face-side connecting terminals connecting therewith and the number of the first and the second capacitor-connecting terminals (the sum of the number of the first capacitor-connecting terminals+(plus) the number of the second capacitor-connecting terminals), and if shortening the wiring of the less number side, the wiring is advantageous with respect to resistance and inductance. Therefore, in case the number of the principal-face-side connecting terminals connected to the first and the second converting-conductor layers is more than the number of the first and the second capacitor-connecting terminals, it is desirable to dispose the first and the second converting-conductor layers as near as possible to the first and the second capacitor-connecting terminals, that is, near to the chip capacitors.
Since the invention selects as the specific interlayer the nearest interlayer to the first capacitor-connecting terminals and the second capacitor-connecting terminals among the interlayers of the mutual insulating layers, there are accordingly nearest disposed the first and the second converting-conductor layers and the first and the second capacitor-connecting terminals. It is possible thereby to reduce resistance and inductance between the principal-face-side connecting terminals and the first, second terminals of the chip capacitors.
In the case of the wiring board mounting IC chips of high integration, the number of the principal-face-side connecting terminals is often many. In IC chips of high integration, lots of source terminals and earth terminals are equipped. Therefore, for mounting IC chips of high integration, it is preferable to apply the invention.
The wiring board is any of the mentioned above, and at least one part of the first capacitor-connecting terminals connected with the first converting-conductor layers at the reverse face side are positioned within such a range of projecting the connected first converting-conductor layers onto the first face, the first capacitor-connecting terminals and the first converting-conductor layers are connected through via-conductors passing the insulating layers, at least one part of the second capacitor-connecting terminals connected to the second converting-conductor layers at the reverse face side are positioned within such a range of projecting the connected second converting-conductor layers onto the first face, and the second capacitor-connecting terminals and the second converting-conductor layers are connected through the via-conductors passing the insulating layers.
In the wiring board of the invention, of the chip capacitors, at least one part of the first capacitor-connecting terminals connected to the first converting-conductor layers are positioned within the range of projecting the connected first converting-conductor layers onto the first face. Reversely to say, seeing from a certain first capacitor-connecting terminal, the first converting-conductor layers connecting thereto positions perpendicularly on the principal face side. The first capacitor-connecting terminals and the first converting-conductor layers are connected through the via-conductors having lower resistance and lower inductance than those of wiring layers formed between the insulating layers, specifically through the via-conductors passing the insulating layers toward the reverse face side from the first converting-conductor layers and extending vertically. Thus, the first capacitor-connecting terminals and the first converting-conductor layers may be connected at low resistance and low inductance.
Similarly, at least one part of the second capacitor-connecting terminals connected to the second converting-conductor layers at the reverse face side are positioned within the range of projecting the connected second converting-conductor layers onto the first face of the chip capacitors. Reversely to say, seeing from a certain second capacitor-connecting terminal, the second converting-conductor layers connecting thereto positions perpendicularly on the principal face side. The second capacitor-connecting terminals and the second converting-conductor layers are connected through the via-conductors passing the insulating layers toward the reverse face side from the first converting-conductor layers and extending vertically. Thus, the second capacitor-connecting terminals and the second converting-conductor layers may be also connected at low resistance and low inductance.
Further, another means for solving the problem is a wiring board having a principal face and a reverse face, comprising a plurality of principal-face-side connecting terminals formed on the principal face side and connectable to respective terminals of electronic parts mounted on the principal face, chip capacitors mounted on the reverse face side furnished with a first electrode and a second electrode composing capacitors, at least one of the chip capacitors having a first face facing to the reverse face, at least one of first terminals formed on the first face and connected to the first electrode, and at least one of second terminals formed on the first face and connected to the second electrode, at least one insulating layer interposed between the principal-face-side connecting terminals and first and second terminals of the chip capacitors, at least one of first converting-conductor layers formed on the reverse face of most-reverse face side insulating layer positioned on the most reverse face side among the insulating layers, connected to the plurality of principal-face-side connecting terminals at the principal face side, connecting directly or via conductive connecting materials with at least one of first terminals at the reverse face side, and changing the connecting positions and the connecting number between the principal face side and the reverse face side, and at least one of second converting-conductor layers formed at the reverse face side of the most-reverse face side insulating layer while being insulating the first converting-conductor layers, connected to the plurality of principal-face-side connecting terminals at the principal face side, connecting directly or via the conductive connecting materials with at least one of second terminals at the reverse face side, and changing the connecting positions and the connecting number between the principal face side and the reverse face side.
The wiring board of the invention is formed at the reverse face side of the most-reverse face side insulating layer with the first and the second converting-conductor layers for changing the connecting positions and the connecting number between the principal face side and the reverse face side. The first converting-conductor layers are connected to the principal-face-side connecting terminals at the principal face side and to the first terminals of the chip capacitors at the reverse face side. Further, the second converting-conductor layers are connected to the principal-face-side connecting terminals at the principal face side and to the second terminals of the chip capacitors at the reverse face side. Therefore, the connection between the principal face side terminals, and the terminals of the electronic parts and the first and second terminals is easily made.
Besides, the first and the second converting-conductor layers are formed at the reverse face side of the most-reverse face side insulating layer among the insulating layers disposed between the principal-face-side connecting terminals and the first, second terminals of the chip capacitors. So, the first and the second terminals of the chip capacitors and the first and the second converting-conductor layers become nearest, so that resistance and inductance occurring therebetween can be reduced to the minimum.
The first and second converting-conductor layers are connected to the first and the second terminals of the chip capacitors directly or via the conductive connecting materials, not via the via-conductors. Therefore, resistance and inductance created by the connection the first and the second terminals of the chip capacitors and the first and the second converting-conductor layers can be reduced to the minimum.
By the way, as the conductive materials, a solder or a conductive adhesive may be taken up. The solder may be selected taking material quality of the wiring board or the first and the second terminals into consideration, for example, there are Pbxe2x80x94Sn based or Snxe2x80x94Sb based solders. As the conductive adhesive, for example, there are those dispersed in resins as epoxy resin with conductive fillers comprising carbon powder, metallic powder as silver, copper or nickel, resin particles covered with these metals, or glass particles.
The wiring board is as mentioned above, and the number of the principal-face-side connecting terminals connected to any of the first converting-conductor layers and the second converting-conductor layers of the principal-face-side connecting terminals is more than the sum of the number of the first terminals connected to the first converting-conductor layers+(plus) the number of the second terminals connected to the second converting-conductor layers.
The wiring of connecting the principal-face-side connecting terminals and the first, second terminals of the chip capacitors can restrain resistance value and inductance, the more the parallel paths. Accordingly, seeing from the first and the second converting-conductor layers, a comparison is made between the number of the principal-face-side connecting terminals connected to these converting-conductor layers and the number of the first and the second capacitor-connecting terminals, and if shortening the wiring of the less number side, the wiring is advantageous with respect to resistance and inductance. Therefore, in case the number of the principal-face-side connecting terminals connected to the first and the second converting-conductor layers is more than the number of the first and the second terminals, it is desirable to dispose the first and the second converting-conductor layers as near as possible to the first and the second terminals, that is, near to the chip capacitors.
In the invention, as mentioned above, the first and the second converting-conductor layers are formed at the reverse face side of the most-reverse face side insulating layer, and are connected to the first and the second terminals of the chip capacitors directly or via the conductive connecting materials, so that the first, second converting-conductor layers and the first, second terminals of the chip capacitors are disposed at the especially near position. Therefore, resistance and inductance between the principal-face-side connecting terminal and the first, second terminals of the chip capacitors can be particularly reduced.
In the case of the wiring board mounting IC chips of high integration, the number of the principal-face-side connecting terminals is often many. Because in IC chips of high integration, lots of source terminals and earth terminals are equipped. Therefore, for mounting IC chips of high integration, it is preferable to apply the invention.
The wiring board is any of the mentioned above, and the first converting-conductor layers and the second converting-conductor layers have parts of stripe patterns alternately arranged.
Of the connecting terminals of electronic parts as IC chip and the principal-face-side connecting terminal in response thereto, those connected to the first terminals of the chip capacitors (for example, those connected to source potential) and those connected to the second terminals (for example, those connected to earth potential) are near and often designed and disposed for parallel parts.
In contrast, the wiring board of the invention has the striped pattern parts in the first and the second converting-conductor layers. In the striped pattern parts, since the first and the second converting-conductor layers are adjacent, the principal-face-side connecting terminal extend the connecting wiring by use of the via-conductors toward the reverse face side in response to the terminals (either of the first terminals and the second terminals) of the chip capacitors, and as needed, the short wiring is formed between the mutual insulating layers so as to adjust the positions for connected to the objective first or second converting-conductor layers. In short, in the striped pattern parts, it is possible to easily connect the principal-face-side connecting terminal with any of the first and the second converting-conductor layers, and the wiring is ready for designing.
In particular, when the first and the second terminals are disposed alternately in the chip capacitors, the first terminals of the chip capacitors can be easily connected to the first converting-conductor layers in the striped pattern parts, while the second terminals of the chip capacitors can be easily connected to the second converting-conductor layers, thereby to make the wiring design easy. Besides, if the first and the second terminals of the chip capacitors are alternately arranged, inductance can be restrained and such arrangement is preferable to the current flowing, since inductance can be lowered by the opposite directions of the currents output from and input in the chip capacitors.
Further, the wiring board is as mentioned above, and the first converting-conductor layers and the second converting-conductor layers have parts where directions of current flowing when charging and discharging the chip capacitors are opposite to each other in the stripe pattern.
The wiring board of the invention has the currents-reverse-flowing parts, and in this part, the currents flowing directions are revered when charging and discharging the chip capacitors and cancel magnetic fields each other (negative mutual inductance occurs). Therefore, in this part, inductance is more restrained and as a whole inductance can be more lowered.
Preferably, there is provided a wiring board according to any one of the paragraphs described above, further having a cavity surrounding portion which is located on the reverse face side from the insulating layer and which constitutes a wall face of a cavity opened on the reverse face side, wherein: the first and second capacitor-connecting terminals are formed on a bottom face of the cavity; and the chip capacitors are mounted in the cavity so that the bottom face of the cavity is opposite to the first faces of the chip capacitors.
In the wiring board according to the invention, chip capacitors each having first and second terminals on its first face are mounted in the cavity. Hence, the chip capacitors are mounted so as to be substantially opposite to electronic parts mounted on the principal face of the wiring board, through the bottom face of the cavity. Hence, the distance between the principal face side connecting terminals of the wiring board and the first and second terminals of the chip capacitors can be shortened and, accordingly, the distance between the electronic parts mounted on the principal face and the chip capacitors can be shortened compared with a double-side laminated wiring board in which no cavity is formed.
Accordingly, the connecting terminals on the principal face side of the wiring board can be connected to the first and second terminals of the capacitors by short paths compared with the double-side laminated wiring board in which no cavity is formed, so that resistance components and inductance components generated on these paths can be suppressed.
Preferably, there is provided a wiring board further having a core substrate including a first core part located on the principal face side, and a second core part located from the first core part on the reverse face side, wherein: the first core part is contained in the insulating layer whereas the second core part is contained in the cavity surrounding portion; the insulating layer includes the first core part located on the most-reverse face side, and one insulating resin layer or a plurality of insulating resin layers laminated on the first core part toward the principal face side; and the cavity surrounding portion includes the second core part, and either no reverse face side insulating layer or reverse face side insulating layers provided on the reverse face side of the second core part so that the number of the reverse face side insulating layers is smaller than the number of the face side insulating resin layers.
In the wiring board according to the invention, one insulating resin layer is provided or a plurality of insulating resin layers are laminated on the principal face side of the first core part, that is, on the principal face side of the core substrate whereas no reverse face side insulating layer is provided or reverse face side insulating layers are provided on the reverse face side of the second core part, that is, on the reverse face side of the core substrate so that the number of the reverse face side insulating layers is smaller than the number of the insulating resin layers. Hence, the wiring board is inexpensive compared with the double-side laminated wiring board because the number of the reverse face side insulating layers can be set to be zero or small.